Method of producing acrylic copolymer

ABSTRACT

A MONOMER MIXTURE CONSISTING ESSENTIALLY OF ACRYLONITRILE, A POLYMERIZABLE VINYL MONOMER MORE HYDROPHOBIC THAN ACRYLONITRILE AND A POLYMERIZABLE VINYL MONOMER MORE HYDROPHILIC THAN ACRYLONITRILE IS POLYMERIZED IN A REACTION MEDIUM CONSISTING OF DIMETHYL SULFOXIDE AND WATER. A RELATIVELY HOMOGENEOUS ACRYLIC COPOLYMER DISPERSION IS OBTAINED WITHIN A RELATIVELY SHORT PERIOD OF TIME AT A HIGH CONVERSION RATIO.

1973 HIROSHI SAKAI AL 3,781,248

METHOD OF PRODUCING ACRYLIC COPOLYMER Filed Aug. 12, 1971 United States Patent O Int. Cl. C08f /76, 15/22 US. Cl. 260-793 M 5 Claims ABSTRACT OF THE DISCLOSURE A monomer mixture consisting essentially of acrylonitrile, a polymerizable vinyl monomer more hydrophobic than acrylonitrile and a polymerizable vinyl monomer more hydrophilic than acrylonitrile is polymerized in a reaction medium consisting of dimethyl ,sulfoxide and water. A relatively homogeneous acrylic copolymer dispersionis obtained within a relatively short period of time at a high conversion ratio.

BACKGROUND OF THE INVENTION 1) Field of the invention This invention is concerned with a novel method of producing a polymer containing acrylonitrile in a state of emulsion from a monomer mixture consisting mainly of acrylonitrile and a polymerizable vinyl monomer which is more hydrophobic than acrylonitrile in a reaction medium consisting essentially of 60-85% by weight of dimethyl sulfoxide and 40-15% by weight of water.

(2) Description of the prior art Heretofore, various processes were suggested for producing copolymer containing acrylonitrile. One such process consisted of carrying out emulsion polymerization in an aqueous medium in the presence of an emulsifier. Another process consisted of carrying out the polymerization in a solvent in which the polymers of the acrylonitrile series are soluble.

In the former process the polymer is salted out and filtered to separate it from the reaction mixture and then dissolved in a solvent. The polymer is then passed through washing, granulation and drying steps to prepare a spinning solution. This process is unsatisfactory because of labor and time required for separation, washing, drying and dissolution. When copolymerizationis conducted in two phases comprised of acrylonitrile and a hydrophobic monomer phase, or three phases comprised of acrylm nitrile phase, a hydrophobic monomer phase, and a hydrophilic monomer phase, the differences in hydrophilic properties of the respective monomers causes the variations in the composition distribution of the polymers in the resulting composition to be substantial, and the processability and physical properties of the polymeric products generally tends to be poor.

In contrast thereto, in the solvent process the polymerization proceeds uniformly in the solvent. There is less variation in the composition distribution of the polymer in the polymeric resulting solution. The polymer may be converted directly into a spinning solution without separation of the polymer.

In British Pat. 928,114 a process is disclosed for preparing an acrylonitrile/vinylidene chloride copolymer in a solvent for a polymer such as dimethyl sulfoxide. However, this process is uneconomical because the polymerization rate is so slow that it takes an excessively long ice time to carry out the polymerization and it is necessary to make the polymerization temperature relatively high. It is difficult to process the polymerization product until polymerization ratio is quite high. In addition, the resulting polymer is highly discolored because the polymerization reaction is carried out at a high temperature for a long time.

Another process has been suggested in Japanese patent publication No. 10,996/1961 for continuously polymerizing a monomer mixture containing at least by weight of acrylonitrile in a mixed medium of dimethyl sulfoxide and water. However, in this process, when the batch polymerization method is employed, the resulting polymer slurry tends to gel at a relatively low concentration of the polymer and cannot be stirred. It'is accordingly essential to carry out the polymerization continuously in this process. However, when the polymerization is carried out continuously according to this process, the concentration of the polymer in the polymer slurry is at most 32% by weight and the polymerization ratio (conversion ratio) is at most 60% which is quite low. Because of the cost required for the recovery and purification of the unreacted monomers, and because the polymerization can only be conducted continuously this process is very inconvenient to employ when relatively small amounts of a given polymer composition are to be I produced.

It is accordingly an object of this invention to 'overcome the aforementioned problems and disadvantages of the prior art processes.

An additional object of the present invention is to obtain an acrylic copolymer emulsion having a high conversion ratio.

Another object of the present invention is to obtain an acrylic copolymer which is excellent in erties and degree of whiteness.

Other objects and advantages of the present invention will become further apparent from a continued reading of the following description.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a photomicrograph showing the polymer obtained by the method of this invention in the dispersed state.

FIG. 2 is a photomicrograph showing the polymer in the dispersed state obtained by a conventional process 7 using a mixture of dimethyl sulfoxide and water as the reaction medium (Japanese patent publication 10,996/ 1961).

FIG. 3 is a photomicrograph showing the polymer in the dispersed state of polymer obtained by a conventional aqueous emulsion polymerization process.

DETAILED DESCRIPTION These objects of the present invention have been achieved by providing a method of producing an acrylic copolymer whichcomprises polymerizing a monomer mix-. 1 ture consisting essentially of (1) 80-19.7% by Weight of acrylonitrile, (2) 19.7-80% by weight of a vinyl physical propmonomer more hydrophobic than acrylonitrile, and (3) at most by weight of a vinyl monomer which is highly hydrophilic in a mixed reaction medium in which the ratio of dimethyl sulfoxide to water is 60:40-85:15 by weight.

It is important that the dimethyl sulfoxide-water reaction medium used in the process of the present invention have a dimethyl sulfoxide-water ratio of 60:40- 85 by weight, preferably 65:35-80:20 by Weight. When the amount of Water in the dimethyl sulfoxidewater reaction medium is less than 15% by weight, even if the polymerization reaction proceeds, a satisfactory emulsion is not produced. The resulting reaction becomes essentially a solution polymerization process. The polymerization rate is slow and the polymerization ratio is likewise low. On the other hand, when the amount of water exceeds 40% by weight, the monomers do not sufliciently dissolve in the reaction medium and a hard granular polymer, which is unsuitable for further processing, is produced. The polymer separates out in the granular state from the polymer emulsion as the reaction proceeds. The ratio of dimethyl sulfoxide to water in the reaction medium i.e. 60/40-85/ 15 by weight, is for the reasons noted above one of the essential features of the method of the present invention.

The reaction medium in addition to containing dimethyl sulfoxide and water may also contain at most 10% by weight of the total mixture of a substance which has mutual solubility in dimethyl sulfoxide and water, such as alcohols, ketones, dimethyl formamide, dimethyl acetamide, a-butyrolactone, and ethylene carbonate.

It is important that the amount of acrylonitrile in the reaction medium of the present invention should be 80- 19.7% by weight and more preferably 65-30% by weight based on the total amount of the monomer mixture. When the content of acrylonitrile exceeds 80% by weight, the content of the hydrophobic vinyl monomer is reduced to an amount at which the reaction mixture solidifies as the polymerization reaction proceeds and becomes impossible to stir.

The content of the hydrophobic polymerizable vinyl monomer in the monomer mixture should be 19.7-80% by weight of the monomer mixture. The hydrophobic vinyl monomer is a monomer whose solubility in water is less than that of acrylonitrile. Typical examples of such monomers are styrene, vinyl acetate, acrylic acid ester such as methyl acrylate and butyl acrylate, methacrylic acid ester such as methyl methacrylate and butyl methacrylate, vinyl ester, vinyl chloride, vinylidene chloride and methacrylonitrile. There are, however, many other suitable hydrophobic vinyl monomers which can be used in the method of this invention as will be obvious to those skilled in the art from a continued reading of the specification.

As the content of the hydrophobic polymerizable vinyl monomer is increased, a lower viscosity emulsion is obtained, despite the fact that the concentration of the polymer in the polymer emulsion is very high. In addition, the stability of the emulsion is increased. Because of this effect, the relative content of the hydrophobic polymerizable vinyl monomer is an important factor in the method of this present invention. When the ratio of the hydrophobic vinyl monomer is less than 19.7% by weight, the polymerization will proceed until the concentration of the polymer reaches a certain concentration and then the reaction mixture will gel and cannot thereafter be stirred. On the other hand, when the ratio of the hydrophobic monomer exceeds 80% by weight, although the viscosity of the polymer emulsion is low, a hard granular polymer tends to be produced in the emulsion.

An amount of 03-10% by weight of a hydrophilic vinyl monomer is also added to the monomer mixture used in the method of this invention. When a monomer mixture consisting of only acrylonitrile and a hydrophobic vinyl monomer is polymerized, as the reaction CH2=C C O O RzS 03M Formula A wherein R stands for H or CH R stands for an alkylene group having 2-6 carbon atoms, a cycloalkylene group having 5-6 carbon atoms or phenylene, M is a member selected from the group consisting of H, Na, K and NR R R R and R R R and R respectively stand for H or an alkyl group having 1-4 carbon atoms. Typical examples are sulfoethyl ester, sulfobutyl ester, sulfocyclohexyl ester, sulfo-(2-ethyl)-hexyl ester, sulfophenyl ester of acrylic acid or methacrylic acid and sodium, potassium, ammonium, and amine salts thereof.

(B) A styrene sulfonic acid or a derivative thereof of the formula:

CH=CH1 S 0 M Formula B wherein X stands for -H, OH, -C1 or an alkyl group having 1-2 carbon atoms and M has the meaning assigned above. Typical examples are 0-, m-, or p-styrene sulfonic acid, 2-chloro-4' vinyl benzene sulfonic acid, 2-methyl-4 vinyl benzene sulfonic acid, 2-hydroxy-4 vinyl benzene sulfonic acid and sodium, potassium, ammonium and amine salts thereof.

(C) A methallyl sulfonic acid or a salt thereof of the formula:

CHzS OaM Formula 0 wherein M has the meaning assigned above. Typical examples are methallyl sulfonic acid and sodium potassium, ammonium, and amine salts thereof.

(D) A methacrylamide derivative of the formula:

X C .H.=i NH ...M

Formula D wherein M and X have the meaning assigned above. Typical examples are p-methacrylamide benzene sulfonic acid, o-hydroxy p-methacrylamide benzene sulfonic acid, mmethyl p-methacryl amide benzene sulfonic acid, o-chloro p-methacrylamide benzene sulfonic acid and sodium, potassium, ammonium and amine salts thereof,

(E) A methallyl ether derivative of the formula CH3 CHg=-CH30- S 03M Formula E wherein M and X have the meaning assigned above. Typical examples are p-methallyl-oxy-benzene sulfonic acid, 0- hydroxy p-methallyl-oxy-benzene sulfonic acid, m-chloro p-methallyl-oxy benzene sulfonic acid ester and sodium, potassium, ammonium and amine salts thereof.

In accordance with the method of the present invention, up to parts by weight of at least one other polymerizable monomer can be added to the monomer mixture if desired.

In the process of the present invention it is very important that the monomer mixture be comprised of at least the three components, namely acrylonitrile, a polymerizable vinyl monomer which is more hydrophobic than acrylonitrile and a hydrophilic vinyl monomer or the salts thereof. In addition it is essential that the respective components be present in the mixture in the aforementioned percentages by weight in the method of the present invention. If such conditions are not satisfied, the objects of the present invention are not obtained.

When a monomer mixture satisfying all of the above conditions is polymerized in a reaction medium consisting essentially of 60-85% by weight of dimethyl sulfoxide and 40-15% by weight of water, an emulsion having very fine polymer particles is obtained using either batch or continuous processes.

Even though the concentration of the polymer is very high, the emulsion that is obtained has a low viscosity, and good stability.

The preferred mixing ratio of dimethyl sulfoxide and water in the reaction medium employed in the method of the present invention is dependent upon the particular hydrophilic monomer employed. The preferable mixing ratios are as follows:

(1) When an acrylic acid or methacrylic acid ester derivative defined by the Formula A is used the mixing ratio of dimethyl sulfoxide and water should be 65 :35- 85: and more preferably 70:30-80:20.

(2) When a styrene sulfonic acid or a derivative thereof defined by the Formula B is used, the mixing ratio of dime'thyl's'ulfoxid'e and water should be 65:35-85:15 and preferably 70:30-80:20.

(3) When methallyl sulfonic acid or a salt thereof shown by the Formula C is used, the mixing ratio of dimethyl sulfoxide and water should be 60:40-80:20 and more preferably 65:35-75:25.

Recently,.the demand for fiber of the acrylonitrile series for use in clothings and interior fabrics such as carpeting, bedding, and drapes, has substantially increased. It has accordingly been necessary to impart flame retardant properties to the acrylonitrile fibers used to make these fabrics. Copolymers of acrylonitrile and vinyl chloride or vinylidene chloride has been proposed for this purpose. The method of the presentinvention is especially well suited for the production of such a flame resistant acrylic copolymer fiber. For example, flame resistant fibers are obtained by polymerizing a monomer mixture consisting essentially of (1) 80-19.7% by weight of acrylonitrile, (2) 19.7-80% by weight of a monomer selected from the group consisting of vinyl chloride, vinylidne chloride and a mixture thereof, and (3) 03-10% by weight of a monomer selected from the group consisting of monomers of Formula A. The acrylic copolymers obtained as a result have excellent fiber forming. and flame retardant properties.

In the present invention, the ratio of the monomer mixture to the solvent when practicing the polymerization process of this invention should be such that the concentration of the monomer mixture in the solvent mixture is not more than 60% by weight and preferably not more than 50% by weight. When the concentration of the monomer exceeds 60% by'weig'ht, gela'tion takes place after the reaction starts and the monomer mixture cannot be stirred. In addition, when the concentration of the monomer is high, the reaction is stopped at a low ratio of polymerization and a polymer emulsion having a low viscosity is obtained. The problem of recovering the unreacted monomer makes the process practical. The method of the present invention may be practiced using a low concentration of the monomer mixture, however, it is preferable that the concentration be at least by weight.

In accordance with the present invention, it is preferable to carry out the reaction in the absence of oxygen since oxygen apparently interferes with the polymerization reaction. Normally, the polymerization is carried out in an inert gas atmosphere such as nitrogen or carbon dioxide.

The polymerization method employed is not critical. The polymerization can be conducted by the batch process, semi-batch process or continuous process and with each process polymer emulsion having good stability, a high polymer concentration and a low viscosity may be obtained.

As a polymerization initiator, an azo compound is normally used as a source for generating a radical, or an organic or inorganic peroxide is used. As an azo compound, oz,0c'-aZObiS (a,a-dimethylvaleronitrile) is effective in terms of the polymerization rate and coloration. As a peroxide, an oxidation-reduction system consisting of an organic peroxide such as aliphatic diacyl peroxides or peroxy esters and a reducing agent, or an oxidationreduction system consisting of a persulfate and sulfurous acid gas. A bisulfate or iron ion is especially effective from the viewpoints of the polymerization ratio and coloration. Further, when iron ion exists in the oxidation-reduction system a preferably result is obtained.

That the polymerization process of the present invention is different from the conventional polymerization process is apparent from the drawings. FIG. 1, which is a photomicrograph showing the dispersed state of the polymer, is obtained by the method of the present invention. As is apparent from this photomicrograph, the polymer is dispersed in a colloidal state and the polymer particles are not agglomerated. For this reason polymerization at a high concentration is possible.

FIG. 2 is a photomicrograph showing a dispersed state of a polymer obtained by polymerizing 93.0% by weight of acrylonitrile, 6.0% by weight of methylacrylate and 1.0% by weight of sodium allylsulfonate in a dimethyl sulfoxide-water (/25) reaction medium. As is apparent from FIG. 2, the polymer particles are agglomerated and accordingly, the viscosity of the dispersion is quite high, which makes it diflicult to obtain a highly concentrated polymer emulsion.

FIG. 3 is a photomicrograph showing the dispersed state obtained by polymerizing 58.0% by weight of acrylonitrile, 40.0% by weight of vinylidene chloride and 2.0% by weight of sulfopropyl methacrylate sodium salt in water containing an emulsifier. As is apparent from FIG. 3, though the polymer particles are dispersed in the water, the polymer particles are somewhat agglomerated so that the viscosity of the emulsion is high.

The polymer emulsion of this invention can be spun into fibers by distilling off water or by adding additional dimethyl sulfoxide to the solution or by concurrently using both methods to provide a spinning solution which can be directly spun into fibers. When the concentration of the polymer in the polymer emulsion is relatively low it is possible to obtain a solution having a viscositysuitable for spinning (above about 50 poises) by distilling off the water in the emulsion. Since this method requires that a relatively large amount of water he distilled off, it requires a considerable amount of heat. On the other hand, when the concentration of the polymer in the polymer emulsion is high, a solution having a viscosity suitable for spinning is easily obtained by diluting the polymer emulsion with dimethyl sulfoxide.

From the viewpoint of the ease of operability of the spinning step and the physical properties of the obtained filaments it is most preferable to dilute a concentrated polymer emulsion with dimethyl sulfoxide and thereafter distill off a part of the water.

According to the process of the present invention, copolymers containing acrylonitrile having excellent properties may be produced very efliciently and economically.

The following examples are given by way of further illustration of the process of the present invention and are not intended to limit the scope of the invention beyond that of the subjoined claims. All parts and percentages in the examples are parts and percentages by weight, not volume, unless otherwise noted.

EXAMPLE 1 Using vinylidene chloride whose solubility in Water is almost zero as the polymerizable hydrophobic vinyl monomer, the influence of the content of vinylidene chloride in a monomer mixture on the properties of a polymer emulsion was determined.

In a 500 cc. glass flask, 40 parts of a monomer mixture consisting of acrylonitrile and vinylidene chloride in amounts expressed by percent in Table 1, and 2% of the sodium salt of methacrylic acid sulfopropylester was added to 60 parts of a mixed dimethyl sulfoxide/water (75/25) reaction medium. 0.1 part of ammonium persulfate, 0.2

drophobic vinylmonomer was increased to 90% as in Run No. 9, the viscosity of the polymer emulsion was still low, but the emulsion was unsatisfactory because hard granules were present in the emulsion.

EXAMPLE 2 TABLE 2 Monomer mixture Properties of the emulsion Polymer- Polymer Methyl- Acrylo- Emulsion ization concenacrylate nitrile viscosity ratio tration (percent) (percent) (centipoise) (percent) (percent) Stability of the emulsion Bun number:

1 98 Gelled 10 min. after the reaction started.

83 Gelled 15 hrs. after the reaction started. 73 3, 800 96. 3 38. 5 Did not gel until 5 days after the reaction ended. 63 530 97. 2 38. 9 Did not gel on 30th day after the reaction ended. 55 43 180 95. 4 38. 2 D0. 70 28 73 98. 0 26. 4 D0. 80 18 54 94. 3 37. 7 Do. 90 8 96. 8 38. 7 Do.

I Could not be measured.

part of sodium bisulfite, 0.01 part of sulfuric acid and 4 EXAMPLE 3 1 p.p.m. of Fe++ was added as the catalyst. The mixture was polymerized batchwise at 40 C. for 4 hours in a nitrogen atmosphere. The properties of the resulting polymer emulsion are shown in Table 1.

Run No. 1 and No. 2 were experiment cases wherein the ratios of vinylidene chloride was less than the specified range of the present invention. When the polymerization reaction proceeded and the concentration of the polymer in the polymer slurry reached a certain point, the reaction contents solidified and could not be stirred.

Example 1 was repeated except that compounds shown in Table 3 were used in place of vinylidene chloride to determine the influence of differences in hydrophobic properties of the vinyl monomer on the properties of the resulting emulsion.

In a 500 cc. glass flask a mixture was charged comprised of 40 parts of a monomer mixture consisting of 43% of acrylonitrile, of another polymeric vinyl monomer and 2% of sodium salt of methacrylic acid sulfopropyl- TABLE 1 Monomer mixture Properties of the emulsion Emulsion Polymer- Polymer Vinylviscosity ization concenidene Acrylo- (centiratio tration chloride nitrile poise) (percent) (percent) Stability of the polymer emulsion 0 98 Gelled 10 min. after the reaction started. 16 83 Gelled 1 hour after the reaction started. 25 73 7, 800 92. 3 26. 9 Did not gel until 5 hours after reaction ended; 35 63 980 92. 1 36. 8 Did not gel until 3 days after reaction ended. 55 43 80 92. 5 37. 0 Was not gelled on 30th day after reaction ended. 28 18 85. 4 34. 2 Do. 18 10 76. 3 30. 5 Do. 8 3 53. 4 21. 4 Do.

1 Could not be measured.

Run Nos. 3-7 were experiments wherein the conditions 70 ester, 60 parts of a mixed dimethyl sulfoxide/water (75/ of the present invention were satisfied. As the ratio of the hydrophobic vinylmonomer was increased, despite the fact that the polymer concentration in the polymer emulsion was very high, low viscosity emulsions were obtained with 25) medium, 0.1 part of ammonium persulfate, 0.2 part of sodium bisulfite, 0.01 part of sulfuric acid and 1 p.p.m. of Fe+++. The mixture was polymerized batchwise at 40 C. for 4 hours in a nitrogen atmosphere. The properties increased stability. However, when the ratio of the hy- 75 of the resulting polymer emulsions are shown in Table 3.

TABLE 3 Properties of the emulsion Polymer Shape Name of a monomer co- Emulsion Polymericoncentrathe em lsipolymerized with viscosity zation ratio tration fied polyacrylonitrile (eentipoise) (percent) (percent) mer Run number:

1 Acrylic acid 2... Hydroxy ethylacrylate 3..- Itaconic acid 4... Vinylideneehloride. 80 92.5 37.0 Good. Methyl acrylate 180 95.4 38.2 o. 6..- Methyl methacrylate 125 92.6 37.0 Do. 7. Styrene 95 96.9 38.8 Do. 8...v Vinyl acetate 130 92.3 3 9 Do.

1 Could not be measured. 1 Gelated until the reaction ended and could not be stirred.

could not be stirred. In contrast thereto, Runs Nos. 4-8

were experiments wherein a polymer and vinyl monomer, more hydrophobic than acrylonitrile was copolymerized. In each of these experiments a polymer emulsion having satisfactory properties'was obtained.

EXAMPLE 4 The eifect of using a salt of acrylic acid sulfoalkyl ester and salt of methacrylic acid sulfoalkyl ester as the hydrophobic vinyl monomer on the properties of a polymer emulsion was evaluated.

In a 500 cc. glass flask a mixture was charged comprised of parts of a monomer mixture having the composition shown in Table4. parts of a dimethyl sulfoxide/water (/25) reaction medium 0.1 part of ammonium persulfate, 0:2'part of sodium bisulfite, 0.01 part 35 of sulfuric acid and 1. p.p.mhof Fe+++. The mixture was polymerized batchwise at 40 C. in a nitrogen atmosphere action proceeded. The reaction system separated into phases, a viscous phase and the reaction medium. An emulsion having dispersed particles of the desired shape was not produced and the polymerization rate and the polymerization ratio were both low. When acrylic acid sulfoalkylester was employed, it resulted in an emulsion whose particle shapes were somewhat poor as compared with the experiment wherein mcthacrylic acid sulfoalkylester was used.

EXAMPLE 5 polymerized batchwise at 40" C. for 4 hours in a nitrogen atmosphere. The properties of the resulting polymer emulsions are shown in Table 5. 7

TABLE 5 Composition oi Pro erties of the cm W on a mixed DMSO/ p um water medium, Emulsion Polymer- Polymer percent viscosity ization concen- (centiratio tration DMSO Water poises) (percent) (percent) Type of emulsion Run number:

5 3,200 45.8 18.2 Uniform solution.

15 2, 300 69. 3 34. 9 Dissolved emulsion. 80 20 360 91. 8 36. 7 Good. 76 25 95. 9 38. 4 Do. 70 30 95 96. 8 38. 7 D0. 65 35 60 98.2 39.3 Solid existed. 60 40 Various solids, separated.

1 Could not be measured.

N OTE.DMSO =Dimethyl sulfoxide.

for 4 hours. The properties of the obtained polymer emulsions are shown in Table 4.

When water was present in the amount of 5% as in Run No. 1, the polymerization mixture became a uni- TABLE 4 Properties of the emulsion Emulsion Polymer- Polymerviscosity ation concen- R n (centiratio tration number Monomer mixture-composition (percent) poise) (percent) (percent) Shape of the polymer in the emulsion 1 Acrylonitrile/vinylidene chloride/SPMA, 43/55/2. 80 92. 5 37. 0 Good. 2. Acrylonitnlelvinyhdene chloride, 44/56 31.6 12.6 Sep orateolii into 2 phases 0! a viscous matter and eme mu. 3, Acrylonitrile/methyl acrylate/SPMA, 43/55/2- 95.4 38.2 Good. 4 Acrylonitn'le/methylacrylate/SPA,43/55/2.t 1,250 e 93. 8 3W5 'Not'gelledon 1st day after reaction ended. 5 Acrylomtnle/methyl acrylate, 44/56 62.3 20. 9 settilaratevln into 2 phases of a viscous matter and eme um.

I Could not be measured.

NorE.-SPMA=Sodium salt of methacrylic acid suliopropylester; SPA=Sodium salt of acrylic acid suliopropylester.

In Run Nos. 1, 3, and 4 when acrylic acid or methform solution. The polymerization rate was very slow acrylic acid sulfoalkylester or a salt was employed as the 70 and the polymerization ratio was low.

hydrophilic monomers thereof and the mixture polymerized, a uniform emulsion having a'preferable shape was obtained. In contrast, in Runs Nos. 2 and 5, when acrylonitrile was copolymerized with only a polymerizable vinyl When the water was 15% or higher as the polymerization reaction proceeded, the polymerization to exhibit the form of emulsion polymerization system. The polymerization rate increased. The polymerization ratio and polymmonomer;-more hydrophilic than acrylonitrile as the re- 75 erization degree increased.

11 12 However, when the water exceeded 40%, as the reperoxide alone, an oxidation-reaction system consisting action proceeded, hard granular polymer particles sepaof peroxide and a reducing agent, and an azo compound rated out of the reaction system and the system could not on the properties of the resulting polymer emulsions was be stirred. Accordingly, it can be seen that the ratio of evaluated. dimethyl sulfoxide/water in the reaction medium is an In a 500 cc. glass flask a mixture was charged comprisimportant factor in the present invention. ing 40 parts of a monomer mixture consisting of 43% of EXAMPLE 6 acrylonitrile, 55% of vinylidene chloride and 2% of sodium salt of methacrylic acid sulfopropylester, 60 parts The efiect of varying the ratio of a monomer mixture of a mixed dimethyl sulfoxide/water (75/25) medium to the dimethyl sulfoxide/water reaction medium on the and 0.01 part of sulfuric acid. To separate samples of properties of a polymer emulsion was evaluated. this mixture, various kinds of polymerization initiators In a 500 cc. glass flask, a mixture was charged comwere added, and the content was polymerized batchwise prised of a monomer mixture consisting of 43% of acryat 40 C. in a nitrogen atmosphere. The properties of the lonitrile, 35% of vinylidene chloride and 2% of sodium obtained polymer emulsions were shown in Table 7.

TABLE 7 Properties of the emulsion Polymer- Polymer- Emulsion ization Polymer ization viscosity time concentra- Coloration Run time (centiratio tion r io number Initiators (1 hr.) poise) (percent) (percent) (percent) 1 0.1 part of ammonium persuifate plus 4 80 92.5 37.0 73. 6

0.2 part of sodium bisulfite plus 1 p.p.m. of Fe 2-.....213. 0.05 part Of a,a'-aZ0biS(a-dimeth- 135 90.1 36.0 71.8

ylvaleronitrile 3 0.05 part oiterbutyl-peroxy pivelate... 20 120 66.3 34.5 65.2

salt of methacrylic acid sulfopropylester, a mixed di- The coloration ratio was obtained by diluting the emulmethyl sulfoxide/Water (75/25) medium, 0.1 part of sion 2.2 times with dimethyl sulfoxide to make it a uniammonium persulfate, 0.2 part of sodium bisulfite, 0.01 form solution. The solution was placed in a 1 cm. thick part of sulfuric acid and 1 p.p.m. of Fe+++. The resulting quartz cell and the percent transmission was measured mixture was polymerized batchwise at C. for 4 hours at 400 m. by a Hitachi visible spectrophotometer with in a nitrogen atmosphere. The properties of the obtained distilled dimethyl sulfoxide as a symmetry liquid and polymer emulsion are shown in Table 6. comparing the measured percentages.

TABLE 6 Properties of the emulsion Monomer/medium ratio Emulsion Polymerviseosity ization Polymer Monomer Medium (centb ratio concen- Stability of the polymer emulsion (part) (part poise) (percent) tration when it was left to stand Run number:

' 10 90 12 90.5 9. 1 Not dgetllled on the 30th day after the reaction en e 20 80 30 91. 8 18. 4 Do. 40 60 80 92.5 37.0 Do. 50 150 91.8 45.9 Not gglled until 7 days after the reaction en e i 40 2,540 92. 9 55. 7 Not gelled until 1 day after the reaction ended. 6 30 Gelled 1 hour after the reaction started and could not be stirred.

1 Could not be measured.

As the concentration of the monomers increased, namely, as the polymer concentration in the polymer 50 From the viewpoint of the polymerization rate and emulsion increased, the emulsion viscosity likewise incoloration, an oxidation-reduction system consisting of creased. When the monomer concentration reached 70%, ammonium persulfate-sodium bisulfite-Fe+++ was most the reaction system gelled 1 hour after the reaction preferable. i

started and could not be stirred. When a high monomer EXAMPLE 8 concentration was employed and the reaction was stopped 55 at a low polymerization ratio, a low viscosity polymer Dimethyl SulfOXide Was added to the P y emulsion emulsion was obtained. However, because of the problem o n in R111} 1 0f g pl 7 to Convert t e e of recovering the unreacted monomer this process was not 810R Into a P1I111111g solutlom The relationship of the considered to be practical amount of dimethyl sulfoxide added to the type of the solution, solution viscosity, possibility of direct spinning, EXAMPLE 7 60 spinnability, and yarn quality is shown in Table 8 below. The efiect of using as a polymerization imtiator, a

' TABLE 8 Adding amount of DMso (9%) gi s gs it h 1 il P ibilit r spiimabmw emulsion Form 01 the solution v ise di r e ct spir m ing Z delilg' 0 White emulsion 0.8 Impossible 20 Separated into gel and emulsion. --do 40 Emulsified viscous slurry do 60 Uniform transparent solution 1,250 Possible Poor.

420 0-... Good. 200 0.... Do. 0-... Do. 50 0-... Do. 13 o Poor.

NorE.--DMSO=Dimethyl sulioxlde:

When the polymer concentration in the polymer emulsion was close to 40%, the dilution of 100 parts of the emulsion with 60-180 parts of dimethyl sulfoxide resulted in a satisfactorily uniform solution for spinning. When the polymer concentration in the polymer emulsion was further reduced by being diluted with additional dimethyl sulfoxide, the viscosity became too low. It was then necessary to distill off water from the polymer emulsion to make it a uniform solution suitable for spinning.

EXAMPLE 9 The properties of a polymer emulsion when semi-batch polymerization was carried out, were evaluated.

In a 1.5 liter flask equipped with a stirrer and a jacket, a mixture was charged comprised of 58 parts of a mixed dimethyl sulfoxide/water (77/23) medium, 0.2 part of sodium bisulfite and 1 p.p.m. of Fe+++.

The temperature was maintained at 40 C. and the flask was sealed with nitrogen.

Thereafter, 42 parts of a monomer mixture (acrylonitrile/vinylidene chloride/ sodium salt of methacrylic acid sulfopropyl ester=50% /48%/2%) and 0.1 part of ammonium persulfate were continuously supplied to said flask over a 2 hours period. After supplying all the monomer and ammonium persulfate, the reaction was continued for an additional 3 hours. The reaction was completed 5 hours after the reaction started.

The characteristic values of the polymer emulsion at the point when the reaction was completed were as follows:

Polymerization ratio percent 91.3 Polymer concentration do 38.3 Emulsion viscosity centipoises 135 Polymer specific viscosity, 115p, 0.596

it was left to stand at room temperature for 30 days, it

still did not gel.

The solution obtained in Run No. 6 of Example 8 (ratio of water content about 6.5%) was named spinning solu- 14 7000 orifices each having a diameter of 0.08 mm. Thereafter the spun filaments were subjected to normal drawing, washing with water, relaxing and drying. The spinning condition and the physical properties of the resulting yarns are shown in Table 9.

From the view point of the spinning condition such as spinnability and stretchability and luster of the obtained yarn, the solution diluted with dimethyl sulfoxide and thereafter distilled to remove water (spinning solution No. 2) was more superior. However, because heat was added upon distilling off water, the degree of whiteness was reduced.

EXAMPLE 11 A mixture of 42 parts of a monomer mixture consisting of of acrylonitrile, 48% of vinylidene chloride, and 2% of sodium salt of methacrylic acid sulfopropylester, 58 parts of a mixed dimethyl sulfoxide/water (78/21) medium 0.2 part of sodium bisulfite and 1 p.p.m. of Fe+++, and a concentrated aqueous solution of 0.1 part of part of ammonium persulfate were continuously supplied at a speed of 2 liters per hour to a continuous polymerization vessel consisting of three 5-liter complete mixing vessels connected in a series. The reaction temperature of each vessel was 40 C. Each vessel was completely sealed with nitrogen. The polymer emulsion which flowed out from a third vessel had a viscosity of 75 centipoises, a polymerization ratio of 89.5% a polymer concentration of 37.6% and a polymer specific viscosity 1 of 0.520. All of these characteristic values were quite satisfactory. The stability of the obtained polymer emulsion was very good.

When approximately the same concentrations of the polymerization initiators and approximately the same temperature-time conditions were adapted, the attained polymerization ratio was the highest by the batch process fol lowed by the semi batch process and the continuous process.

EXAMPLE 12 The effect of styrene sulfonic acid or a derivative thereof or a salt thereof as the hydrophilic component on the properties of a polymer emulsion was evaluated.

In a 500 cc. glass flask, 40 parts of a monomer mixture having the composition shown in Table 12, 60 parts of a mixed dimethyl sulfoxide/water (75/25) medium, 0.1 part of ammonium persulfate, 0.2 part of sodium bisulfite, 0.01 part of sulfuric acid and 1.5 p.p.m. of Fe were charged. The reaction mixture polymerized batchwise at 40 C. for 4 hours in a nitrogen atmosphere. The properties of the resulting polymer emulsions are shown in Table 12 below.

TABLE 12 Properties of the emulsion Emulsion Polymer- Polymer viscosity ization concen- Run (centiratio tration number Monomer mixturecomposition (percent) poise) (percent) (percent) Type of the emulsion 1 Airyfilonitlilelvinylidene chloride 12-Me-p-SSS, 85 93. 8 37. 5 Good. 2. Acrylonitrile/vinylidene chloride, 44/56 31. 8 12. 6 38138131286 into 2 phases of a viscous matter and the me um. Airayslgritrilelmethyl aerylate 12-Me-p-SSS, 230 94. 7 37. 9 Good. 4 Acryloni trilelmethyl acrylate 44/56 52. 3 20. 9 separaited into 2 phases of a viscous matter and the me um.

I Could not be measured.

NorE.2-Me-p-SSS=Sodium salt of 24nethyl-4-vinyl benzenesulionic acid.

tion No. 1 and a solution obtained by treating said spinning solution No. 1 in an evaporator to distill off water under a reduced pressure of 40 mm. Hg until the ratio of water content was about 2% and was named spinning solution No. 2 (viscosity 315 poises).

After these two spinning solutions were filtered and defoamed, the solutions were spun into a 50% aqueous In Runs Nos. 1 and 3 styrene sulfuric acid or a derivative thereof for a salt thereof as the hydrophilic monomer was copolymerized and a uniform emulsion was obtained. In contrast, in Runs Nos. 2 and 4, in which acrylonitrile was copolymerized with a more hydrophobic polymerizable vinyl monomer than acrylonitrile as the reaction proceeded, the reaction system was separated into two phases,

solution of dimethyl sulfoxide from a spinneret having a viscous phase and the reaction medium. An emulsion 15 having a satisfactory dispersion was not obtained. The polymerization rate and the polymerization ratio were both low.

From the similar experiment, it was recognized that when derivatives of styrene sulfonic acid other than 2- methyl-4-vinylbenzene sulfonic acid and a salt there were used, similar results as noted above were obtained. However, when p-styrenesulfonic acid, 2-methyl-4-vinylbenzenesulfonic acid and a salt thereof were used the type of emulsions were excellent.

From the viewpoint of the spinning situations such as spinnability and stretchability, and luster of the obtained yarn, the solution diluted with dimethyl sulfoxide and distilling 01f water (spinning solution No. 2) was more preferable. However, because heat was added upon distilling off water, the degree of whiteness lowered and therefore some attention was required.

EXAMPLE 13 A mixture of 42 parts of a monomer mixture consisting of 50% of acrylonitrile, 48% of vinylidene chloride and 2% of sodium methallylsulfonate, 38 parts of a mixed dimethyl sulfoxide/water (74/26) medium, 0.2 part of sodium bisulfite and 1 p.p.m. of Fe+++, and a concentrated aqueous solution of 0.1 part of ammonium persulfate were continuously supplied at a speed of 2 liters per hour to a continuous polymerization vessel consisting of three -liter complete mixing vessels connected in series. The reaction temperature at each vessel was 40 C. Each vessel was completely sealed with nitrogen. A polymer emulsion flowed out from a third vessel and had a viscosity of 90 centiposies, a polymerization ratio of 83.8%, a polymer concentration of 35.2% and a polymer specific viscosity nm of 0.501, and all of these characteristic values were satisfactory. The stability of the obtained polymer emulsion was very good.

When roughly the same concentrations of the initiators and roughly the same temperature-time conditions were adopted, the attained polymerization ratio was the highest by the batch process, followed by the semi-batch process and the continuous process.

EXAMPLE 14 To a glass flask (500 cc.), 40 parts by weight of monomer mixture consisting of 58% by weight of acrylonitrile, 40% by weight of methylmethacrylate and 2% by weight of p-methallylamide benzene sulfonic acid sodium salt, 60 parts by weight of reaction medium consisting of 75% by weight of dimethyl sulfoxide and 25% by weight of water, 0.1 part by weight of ammonium persulfate, 0.2 part by weight of sodium bisulfite, 0.01 part by weight of sulfonic acid and 1 ppm. of Fe+++ were added. The mixture was reacted at about 50 C. for 3 hours under nitrogen atmosphere.

The results are shown as follows:

EXAMPLE 15 The same procedure as Example 14 was repeated except using p-methacryl oxy benzene sulfonic acid sodium salt instead of using p-methacrylamide benzene sulfonic acid sodium salt.

The results are shown as follows:

Viscosity of polymer emulsion ...centipoises 121 Concentration of polymer in the emulsion percent by weight..- 37.4 Conversion do 93.5

Stability of the emulsion Good What is claimed is:

1. A method of producing an acrylic copolymer comprising polymerizing a monomer mixture consisting essentially of (1) -19.7% by Weight acrylonitrile, (2) 19.7- 80% by weight of a hydrophobic vinyl monomer selected from the group consisting of styrene, vinyl acetate, vinyl ether, vinyl chloride, vinylidene chloride, methacrylonitrile, and acrylic acid ester having 5-12 carbon atoms and mixtures thereof, and (3) 03-10% by weight of a hydrophilic vinyl monomer selected from the group consisting of:

(A) an acrylic monomer of the formula:

Rt CH|=C/ ODOR-1S 03M (B) a styrene derivative of the formula:

CH=CH1 801M (C) a methallyl monomer of the formula:

cm=o

c aSOxM (D) a methacrylamide derivative of the formula:

(E) a methallyl ether of the formula:

(F) mixtures thereof, wherein R is H of CH R is a member selected from the group consisting of alkylene groups having 2-6 carbon atoms, cycloalkylene groups having 5-6 carbon atoms, and phenylene; and M is H, Na, K or NR R R R where R R R and R each represent H or an alkyl having l-4 carbon atoms and X is H, OH, C1, or alkyl having 1-2 carbon atoms in a reaction medium consisting essentially of -60% by weight of dimethyl sulfoxide and 15-40% by weight of water.

2. The method of producing acrylic copolymers according to claim 1 which comprises polymerizing a monomer mixture consisting essentially of (1) 80-19.7% by Weight of acrylonitrile, (2) l9.780% by weight of a vinyl monomer selected from the group consisting of styrene, vinyl acetate, vinyl ether, vinyl chloride, vinylidene chloride, methacrylonitrile, acrylic acid ester of alcohol having 1-8 carbon atoms, methacrylic acid ester of alcohol having 1-8 carbon atoms and mixtures thereof, and (3) 03-10% by weight of an acrylic monomer of the formula:

wherein R is H or CH R is a member selected from carbon atoms and phenylene, and M is H, Na, K or NR R R R where R R R and R each represent H or alkyls having 1-4 carbon atoms, in a reaction medium consisting essentially of 85-65% by weight of dimethyl sulfoxide and 15-35 by Weight of water.

3. The method of producing acrylic copolymers according to claim 1 which comprises polymerizing a monomer mixture consisting essentially of (1) 8019.7% by weight of acrylonitrile, (2) 19.7-80% by weight of vinyl monomers selected from the group consisting of styrene, vinyl acetate, vinyl ether, vinyl chloride, vinylidene chloride, methacrylonitrile, acrylic acid ester of alcohol having 1-8 carbon atoms, methacrylic acid ester of alcohol having l-8 carbon atoms and mixtures thereof, and (3) 03-10% by weight of a styrene derivative of the formula:

CH=CH1 wherein X is H, OH, C1 or alkyl having 1-2 carbon atoms and M is H, Na, K or NR R R R Where R R R and R each represent H or alkyls having 1-4 carbon atoms, in a reaction medium consisting essentially of 85-65% by weight of dimethyl sulfoxide and 15-35% by weight of water.

4. The method of producing acrylic copolymers according to claim 1 which comprises polymerizing a monomer mixture consisting essentially of (1) 80-19.7% by weight of acrylonitrile, (2) 19.7% by weight of a vinyl monomer selected from the group consisting of styrene, vinyl acetate, vinyl ether, vinyl chloride, vinylidene chloride, methacrylonitrile, acrylic acid ester of alcohol having l-8 carbon atoms, methacrylic acid ester of alcohol having 1-8 carbon atoms, and mixtures thereof, and (3) 0.3- 10% by weight of a methallyl monomer of the formula:

/CH1 CH1:

CH S O M wherein M is H, Na, K, or NR R R R where, R R R and R each represent H or an alkyl having 1-4 carbon atoms, in a reaction medium consisting essentially of 80- 60% by weight of dimethyl sulfoxide and 20-40% by weight of water.

5. The method of producing fiber forming and flame retardant acrylic copolymers according to claim 1 which comprises polymerizing a monomer mixture consisting essentially of (1) 80-19.7% by weight of acrylonitrile, (2) 1'9.7-80% by weight of a monomer selected from the group consisting of vinyl chloride, vinylidene chloride, and mixtures htereof and (3) 03-10% by weight of hydrophfilic vinyl monomer selected from the group consistmg 0 (A) an acrylic monomer of the formula:

R1 CHz=C COORQSOIM (B) a styrene derivative of the formula:

sonu

(C) a methallyl monomer of the formula:

CH1=C cmsolivr (D) a methacryl amide derivative of the formula:

(E) a methallyl ether of the formula:

References Cited UNITED STATES PATENTS 2/1969 Masson 260--895 3,310,535 3/1967 Mazzolini et a1 260-785 3,515,705 6/1970 Balitrand 26085.5

LESTER L. LEE, Primary Examiner US. Cl. X.R.

260-29.6 TA, 29.6 AN, 49, 80.5, 85.5 ES, 85.5 NC, 85.5 XA

UNITED STATES PA 'l-ENT OFFICE CERTIFICATE OF CORRECTION Patent NO. 3,781,248 Dated December 25, 1973 lnventofls) Hiroshi Sakai et a] It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 31, delete "a-butyrolactone" and substitute X -butyrolactone-.

Column 4, lines 61-63 delete "o-hydroxy p-methacrylamide benzene sulfonic acid, m-methyl pmethacryl amide benzene sulfonic acid, o-chloro p-methacrylamide" and substitute ---2hydroxyA-methacrylamide benzene sulfonic acid, 3 methyl-4-methacryl amide benzene sulfonic acid, Q Z-chlorormethacrylamide Column 6, line 16, delete "(a,a' -dimethylvale ronitri1e)" and substitute--(a,X-dimethylvaleronitrile)--.

Column 6, line 22, after the words "acid gas" please insert -may be used-'.

Columns 7 and 8, Tables 1 and 2, Run number 7, delete "8O 18" and substitute -76 22--.

a F O H/1 5 0-1050 {10-69) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 781 248 Dated December 25 1973 Page 2 ln fl Hiroshi Sakai et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 11, line 13, delete "35% of" and substitute "-5570 of-.

Columns 11 and 12 Table 7, Run number 2 delete xdimethyl valeronitrile)" and substitute --(a ,bdimethylvaleronitrile)-e-.

Columns ll gld l2 Table 8, in the title delete "Adding amount of DMSO (9%)" and substitute --Add'jng amount of DMSO parts--.

Column 13, Table 9 in the title delete "Spinnability (m. /meter)" and substitute -Spinnability (meters/minJ- -e Columns 13 and 14, Table 12, Run numbers 1 and 3, delete "l2-Me-p-SSS," and substitute 2-Me-p-SSS, 7

Column 14, line 68, delete "sulfuric" and substitute -sulfonic-- Signed and sealed this 23rd day of July 1971+- (SEAL) Attest: Y

McCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-1050(10-69) 

